Thank you @Vamp898. I bought a new pair of FA9 recently, convinced by your posts. I couldn't try it beforehand so just ordered and crossed my fingers. So far, I'm really happy with it, from details, tonal reproduction to sound separation. It's a solid upgrade from my previous daily driver XBA-A3.

I'm lucky to hear that. My personal recommendation is to use the Bass Eartips and use the Bass Boost (all's switches down) or Pop setting (down, up, down, depending on your music connection).

And when your insert them, don't push them in. Just let them slip into your ear (while pulling the ear up or back) so they don't built-up pressure.

But the FiiO FA9 sounds very different than the XBA-A3 and it needs a natural source to shine.

Thank you again for your recommendation. I took time to try out different settings and eartips and those changed the sound much more than what I expected. I think I like both bass boost tuning (all down) and pop (down up down) but I just leave it at all-down now as the treble, while well balanced, can be a tiny bit bright for my taste and can be tiresome after long listening sessions.

I don't know if I imagined this but when I used the bass tips, bass seemed to be reduced rather than boosted up like the name implied. For now I settled with the balanced tips (they sounds like spinfit or memory foam, but a little bit more comfy). Balanced tips fits reasonably well and more convenient so I don't have to use memory foam.

As for the XBA-A3 I think I need to explain a bit to do it justice. XBA-A3 was my daily driver and I still listening to it regular now even after I got my FA9. I love its sound. The thing is it is not a balanced sounding pair so sometimes it makes particular recordings sound weird. For example in Queen's "Bohemian Rhapsody", because of the bass boost, the bass in verse 1 stand out a bit too much that it doesn't make sense musically. Sometimes it does change the characteristic of the song, like in the beginning of "Mach dich frei" by Finsterforst, the treble was shadowed by the bass presentation and it changes the wilderness imagination into something like a journey to the deep, I don't know if that makes sense. Those and similar things that made me to find another pair of IEM with more (neutral? accurate?) tuning. Something like my HD650.